全文获取类型
收费全文 | 1475篇 |
免费 | 57篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 21篇 |
综合类 | 9篇 |
化学工业 | 276篇 |
金属工艺 | 13篇 |
机械仪表 | 20篇 |
建筑科学 | 75篇 |
矿业工程 | 5篇 |
能源动力 | 38篇 |
轻工业 | 108篇 |
水利工程 | 19篇 |
石油天然气 | 9篇 |
无线电 | 164篇 |
一般工业技术 | 296篇 |
冶金工业 | 285篇 |
原子能技术 | 11篇 |
自动化技术 | 189篇 |
出版年
2023年 | 13篇 |
2022年 | 23篇 |
2021年 | 43篇 |
2020年 | 30篇 |
2019年 | 29篇 |
2018年 | 24篇 |
2017年 | 23篇 |
2016年 | 28篇 |
2015年 | 28篇 |
2014年 | 25篇 |
2013年 | 79篇 |
2012年 | 64篇 |
2011年 | 82篇 |
2010年 | 76篇 |
2009年 | 42篇 |
2008年 | 59篇 |
2007年 | 59篇 |
2006年 | 54篇 |
2005年 | 47篇 |
2004年 | 29篇 |
2003年 | 39篇 |
2002年 | 25篇 |
2001年 | 16篇 |
2000年 | 24篇 |
1999年 | 31篇 |
1998年 | 87篇 |
1997年 | 51篇 |
1996年 | 49篇 |
1995年 | 37篇 |
1994年 | 26篇 |
1993年 | 32篇 |
1992年 | 14篇 |
1991年 | 15篇 |
1990年 | 16篇 |
1989年 | 10篇 |
1987年 | 9篇 |
1986年 | 16篇 |
1985年 | 15篇 |
1984年 | 13篇 |
1983年 | 13篇 |
1982年 | 11篇 |
1981年 | 14篇 |
1980年 | 16篇 |
1979年 | 14篇 |
1978年 | 8篇 |
1977年 | 13篇 |
1976年 | 13篇 |
1975年 | 7篇 |
1973年 | 9篇 |
1972年 | 8篇 |
排序方式: 共有1538条查询结果,搜索用时 15 毫秒
1.
Robert Groth Luke T. Cravigan Sadegh Niazi Zoran Ristovski Graham R. Johnson 《Journal of the Royal Society Interface》2021,18(178)
The airborne dynamics of respiratory droplets, and the transmission routes of pathogens embedded within them, are governed primarily by the diameter of the particles. These particles are composed of the fluid which lines the respiratory tract, and is primarily mucins and salts, which will interact with the atmosphere and evaporate to reach an equilibrium diameter. Measuring organic volume fraction (OVF) of cough aerosol has proved challenging due to large variability and low material volume produced after coughing. Here, the diametric hygroscopic growth factors (GF) of the cough aerosol produced by healthy participants were measured in situ using a rotating aerosol suspension chamber and a humidification tandem differential mobility analyser. Using hygroscopicity models, it was estimated that the average OVF in the evaporated cough aerosol was 0.88 ± 0.07 and the average GF at 90% relative humidity (RH) was 1.31 ± 0.03. To reach equilibrium in dry air the droplets will reduce in diameter by a factor of approximately 2.8 with an evaporation factor of 0.36 ± 0.05. Hysteresis was observed in cough aerosol at RH = ∼35% and RH = ∼65% for efflorescence and deliquescence, respectively, and may depend on the OVF. The same behaviour and GF were observed in nebulized bovine bronchoalveolar lavage fluid. 相似文献
2.
Hambleton P.J. Ng B.K. Plimmer S.A. David J.P.R. Rees G.J. 《Electron Devices, IEEE Transactions on》2003,50(2):347-351
The nonlocal enhancement in the velocities of charge carriers to ionization is shown to outweigh the opposing effects of dead space, increasing the avalanche speed of short avalanche photodiodes (APDs) over the predictions of a conventional local model which ignores both of these effects. The trends in the measured gain-bandwidth product of two short InAlAs APDs reported in the literature support this result. Relatively large speed benefits are predicted to result from further small reductions in the lengths of short multiplication regions. 相似文献
3.
Twenty-six patients with an intracardiac myxoma underwent surgical resection at our institution from 1977 through 1992. Left atrial myxoma was diagnosed in 22 patients, left ventricular in 1, right atrial in 2, and right ventricular in 1. Six patients were asymptomatic; preoperative symptoms included dyspnea, arrhythmias, embolic episodes, and syncope. The diagnosis was established with transthoracic echocardiography in all cases but one. Surgery was performed in all cases with the aid of cardiopulmonary bypass with moderate hypothermia and cold crystalloid cardioplegia. One patient with a left ventricular myxoma died in a comatose state during the immediate postoperative period. Long-term clinical and echocardiographic evaluation was performed in 19 patients; results were excellent (all the patients were in New York Heart Association functional class I or II), and no recurrences were documented. The clinical characteristics, diagnostic methods, and surgical approach are presented and discussed. 相似文献
4.
The superior high temperature mechanical strength and oxidation resistance of ferritic oxide dispersion strengthened (ODS) tubular alloys are compromised by the difficulties encountered in joining. Conventional fusion welding techniques generate a weld fusion zone which is devoid of the mechanical strength exhibited by the base material. Therefore, more sophisticated solid state joining techniques, such as diffusion bonding, must be employed when joining ODS materials. This paper describes a series of solid state diffusion bonding experiments carried out between two tubular ferritic ODS alloys and two high temperature austenitic alloys. Careful control of bonding conditions produced pressure retaining joints between one of the tubular ODS alloys and both austenitic alloys. The successful joint design was incorporated into the manufacture of a tubular creep component, which enabled a series of internally pressurized creep tests to be carried out. The microstructure developed at the bond interface of each of the four separate material couples is described and the high temperature performance of the pressure retaining joints is discussed. 相似文献
5.
6.
FV Elmslie M Rees MP Williamson M Kerr MJ Kjeldsen KA Pang A Sundqvist ML Friis D Chadwick A Richens A Covanis M Santos A Arzimanoglou CP Panayiotopoulos D Curtis WP Whitehouse RM Gardiner 《Canadian Metallurgical Quarterly》1997,6(8):1329-1334
The epilepsies are a group of disorders characterised by recurrent seizures caused by episodes of abnormal neuronal hyperexcitability involving the brain. Up to 60 million people are affected worldwide and genetic factors may contribute to the aetiology in up to 40% of patients. The most common human genetic epilepsies display a complex pattern of inheritance. These are categorised as idiopathic in the absence of detectable structural or metabolic abnormalities. Juvenile myoclonic epilepsy (JME) is a distinctive and common variety of familial idiopathic generalised epilepsy (IGE) with a prevalence of 0.5-1.0 per 1000 and a ratio of sibling risk to population prevalence (lambda(s)) of 42. The molecular genetic basis of these familial idiopathic epilepsies is entirely unknown, but a mutation in the gene CHRNA4, encoding the alpha4 subunit of the neuronal nicotinic acetylcholine receptor (nAChR), was recently identified in a rare Mendelian variety of idiopathic epilepsy. Chromosomal regions harbouring genes for nAChR subunits were therefore tested for linkage to the JME trait in 34 pedigrees. Significant evidence for linkage with heterogeneity was found to polymorphic loci encompassing the region in which the gene encoding the alpha7 subunit of nAChR (CHRNA7) maps on chromosome 15q14 (HLOD = 4.4 at alpha = 0.65; Z(all) = 2.94, P = 0.0005). This major locus contributes to genetic susceptibility to JME in a majority of the families studied. 相似文献
7.
Electronic BITE is poor at identifying hardware failure and in present design approaches tends to create the reviled ‘unconfirmed failure’. A different approach to BITE and unconfirmed failure could improve both operational performance and the cost of maintenance. 相似文献
8.
9.
D.P. Rees 《Journal of Stored Products Research》1985,21(3):115-118
The life history and behaviour of Teretriosoma nigrescens Lewis are typical of a histerid predator, but only 2, instead of the expected 3, larval instars were recorded. At 27°C, 70% r.h. development from oviposition to adult emergence took about 8 weeks. In 24 h at 27°C, 70% r.h., T. nigrescens adults and larvae, respectively, consumed on average up to 1.7 and 3.5 Prostephanus truncatus (Horn) larvae. After 7 weeks, 10 T. nigrescens adults prevented populations of 25, 50, 75 and 100 P. truncatus from increasing, while controls increased at least 10-fold. Grain moisture contents of between 8.5–14% had little effect on predatory efficiency. 相似文献
10.
Yan T Wong Norbert Dommel Philip Preston Luke E Hallum Torsten Lehmann Nigel H Lovell Gregg J Suaning 《IEEE transactions on neural systems and rehabilitation engineering》2007,15(3):425-434
A neurostimulator application-specific integrated circuit (ASIC) with scalable circuitry that can stimulate 14 channels, has been developed for an epi-retinal vision prosthesis. This ASIC was designed to allow seven identical units to be connected to control up to 98 channels, with the ability to stimulate 14 electrodes simultaneously. The neurostimulator forms part of a vision prosthesis, designed to restore vision to patients who have lost their sight due to retinal diseases such as retinitis pigmentosa and macular degeneration. For charge balance, the neurostimulator was designed to stimulate with current sources and sinks operating together, and with the ability to drive a hexagonal mosaic of electrodes to reduce the electrical crosstalk that occurs when multiple bipolar stimulation sites are active simultaneously. A hexagonal mosaic of electrodes surrounds each stimulation site and has been shown to effectively isolate each site, increasing the ability to inject localized independent charge into multiple regions simultaneously. 相似文献